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Mathematics

If A =[3112],\text{If A }= \begin{bmatrix}[r] 3 & 1 \ -1 & 2 \end{bmatrix}, then A2 =

  1. [8553]\begin{bmatrix}[r] 8 & 5 \ -5 & 3 \end{bmatrix}

  2. [8553]\begin{bmatrix}[r] 8 & -5 \ 5 & 3 \end{bmatrix}

  3. [8553]\begin{bmatrix}[r] 8 & -5 \ -5 & -3 \end{bmatrix}

  4. [8553]\begin{bmatrix}[r] 8 & -5 \ -5 & 3 \end{bmatrix}

Matrices

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Answer

Given,

A=[3112]A2=[3112][3112]=[3×3+1×(1)3×1+1×2(1)×3+2×(1)(1)×1+2×2]=[913+2321+4]=[8553]A2=[8553].\text{A} = \begin{bmatrix}[r] 3 & 1 \ -1 & 2 \end{bmatrix} \\[0.5em] \Rightarrow \text{A}^2 = \begin{bmatrix}[r] 3 & 1 \ -1 & 2 \end{bmatrix}\begin{bmatrix}[r] 3 & 1 \ -1 & 2 \end{bmatrix} \\[0.5em] = \begin{bmatrix}[r] 3 \times 3 + 1 \times (-1) & 3 \times 1 + 1 \times 2 \ (-1) \times 3 + 2 \times (-1) & (-1) \times 1 + 2 \times 2 \end{bmatrix} \\[0.5em] = \begin{bmatrix}[r] 9 - 1 & 3 + 2 \ -3 - 2 & -1 + 4 \end{bmatrix} \\[0.5em] = \begin{bmatrix}[r] 8 & 5 \ -5 & 3 \end{bmatrix} \\[0.5em] \therefore \text{A}^2 = \begin{bmatrix}[r] 8 & 5 \ -5 & 3 \end{bmatrix}.

∴ Option 1 is the correct option.

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